Method for controlling error of internet fax data

ABSTRACT

Provided are a method for controlling errors of an Internet fax data according to the statue of a network by using a receiver report (RR) message in a real-time transport control protocol (RTCP) and a gateway to which the method is applied. Therefore, transmission errors are reduced and a transmission speed of a fax data is improved in transmitting a fax data over the Internet. The provided method includes receiving a T.38 fax data for analyzing a predetermined QoS motoring data of the T.38 fax data and generating status information, transmitting the status information to a gateway which has transmitted the T.38 fax data, receiving the status information for analyzing a packet loss of the transmitted T.38 fax data based on the status information, and increasing or decreasing a secondary message sequence length based on an analysis result. The provided method can control errors of a T.38 packet in real time, according to the status of a network, in transmitting a T.38 fax data over the Internet. Therefore, the performance of an error control improves, thereby securing a stable communication and improving a transmission speed. As a result, a communication speed increases so that transmission efficiency improves.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for reducing errors intransmitting a fax data over the Internet, and more particularly, to amethod for controlling errors of an Internet fax data according to thestatue of a network by using a receiver report (RR) message in areal-time transport control protocol (RTCP) and a gateway to which themethod is applied.

2. Description of the Related Art

Korean Laid-open Patent No. 1999-0051938 discloses an apparatus and amethod for restoring an image to restore an image of a fax datadistorted in transmitting the fax data. In this case, when an erroroccurs in a received fax data, the apparatus decides a modulation methodfor transmitting and receiving the fax data so as to read out aplurality of error patterns according to the decided modulation methodand to monitor errors in the received fax data, line-by-line.Thereafter, if an error occurred in a line, the apparatus corrects theerror by using the error pattern to provide a high quality image to auser.

Korean Laid-open Patent No. 1999-0086290 discloses an apparatus and amethod for checking a transmission status of a fax data. In this case,when a sender, which has transmitted a fax data, requires a voice demandfunction, a recipient automatically services a reception status of thefax data. Thus, the sender conveniently recognizes the transmissionstatus of the fax data. In addition, the recipient services othermessages to improve reliability of the transmission of the fax data.

However, conventional apparatuses and methods concern with thetransmission of a fax data only over a telephone network using aconventional T.30 protocol. Therefore, the conventional apparatuses andmethods cannot be applied to the transmission of a fax data using a T.30protocol. Furthermore, in the conventional methods, a method for anerror control in the transmission of a fax data is fixed; therefore,reliability of the transmission of a fax data is lowered when the statusof a telephone network is deteriorated.

SUMMARY OF THE INVENTION

To solve the above-described problems, it is an objective of the presentinvention to provide a method for a network adaptive error controlaccording to the status of a network, in transmitting a fax data overthe Internet by using a T.38 protocol and a gateway to which the methodis applied.

To accomplish the above objective of the present invention, a gatewayaccording to the present invention includes a first protocol processunit transmitting and receiving an H.323 call setup data, a secondprotocol process unit generating status information on a fax data basedon the fax data transmitted and received between gateways by using areal-time transport protocol, a third protocol process unit receivingthe status information for analyzing the status of a network andselecting a method for controlling errors, and a connection unitconverting a predetermined protocol data for the FoIP including theH.323 call setup data into a data architecture appropriate to a packetswitching network for transmitting and receiving the converted data toand from the packet switching network.

To accomplish the above objective of the present invention, a method forcontrolling errors of an Internet fax data includes receiving a T.38 faxdata, analyzing a predetermined quality of service (QoS) monitoring dataof the T.38 fax data, and transmitting the analysis result of the act(b) to the gateway which has transmitted the T.38 fax data.

To accomplish the above objective of the present invention, a method forcontrolling errors of an Internet fax data includes receiving analysisinformation on a T.38 fax data which has transmitted, from a gateway,analyzing a packet loss of the transmitted T.38 fax data based on theanalysis information, and increasing or decreasing a secondary messagesequence length based on the analysis result.

To accomplish the above objective of the present invention, a method forcontrolling errors of an Internet fax data includes receiving a T.38 faxdata for analyzing a predetermined QoS motoring data of the T.38 faxdata and generating status information, transmitting the statusinformation to a gateway which has transmitted the T.38 fax data,receiving the status information for analyzing a packet loss of thetransmitted T.38 fax data based on the status information, andincreasing or decreasing a secondary message sequence length based on ananalysis result.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objective and advantages of the present invention will becomemore apparent by describing in detail a preferred embodiment thereofwith reference to the attached drawings in which:

FIG. 1 is a diagram of a gateway to which a method for controllingerrors of an Internet fax data according to the present invention isapplied;

FIG. 2 is a diagram illustrating the constitution of a T.38 packet;

FIG. 3 is a diagram for illustrating the constitution of a receiverreport (RR) message of a real-time transport control protocol (RTCP) intransmitting and receiving an Internet fax data between gateways; and

FIG. 4 is a flowchart for explaining a method for controlling errors ofan Internet fax data according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a diagram of a gateway to which a method for controllingerrors of an Internet fax data according to the present invention isapplied, and FIG. 2 is a diagram illustrating the constitution of a T.38packet.

The blocks of a gateway 100 for transmitting and receiving an Internetfax data will now be described. Here, the gateway 100 is a terminaldevice providing a bi-directional communication between an H.323terminal or a gateway on a local area network (LAN) and an InternationalTelecommunication Union (ITU) terminal on a wide area network (WAN) inreal time. A first protocol process unit 130 sends, receives, andprocesses an H.323 call setup data, which is transmitted into thegateway 100. An H.323 protocol is a multimedia communication systemstandard which supports audio and video data in a packet-based networkincluding the Internet, where the standardization is formulated by theInternational telecommunication Union-Telecommunication StandardizationSector (ITU-T). The first protocol process unit 130 processes H.225.0(call signaling protocols and media stream packetization forpacket-based multimedia communication systems) registration, admission,and status (RAS), H.225.0 Q931, and H.245 messages.

A second protocol process unit 150 analyzes and processes a quality ofservice (QoS) monitoring data, such as packet loss and jitter of a faxdata which is transmitted and received between the gateways 100, basedon a real-time transport control protocol (RTCP), and reports analysisresults to a third protocol process unit 170.

The third protocol process unit 170 selects a method for controllingerrors based on the QoS monitoring data transmitted from the secondprotocol process unit 150. A procedure for a method for controllingerrors will now be described in detail. The third protocol process unit170 performs conversions between a T.30 data and a T.38 data. In otherwords, the third protocol process unit 170 converts a T.30 datatransmitted via a public switched telephone network (PSTN) into a T.38data and transmits the T.38 data to a connection unit 110 to interlockwith the PSTN. In addition, the third protocol process unit 170 receivesa T.38 data transmitted over the packet network by using the connectionunit 110 and converts the T.38 data into a T.30 data to interlock withthe PSTN.

The function of the connection unit 110 is divided into conversion of anupper protocol data and conversion of an upper data. Here, theconnection unit 110 converts the upper protocol data, such as H.323,RTCP, and T.38, into a transmission control protocol (TCP) data or auser datagram protocol (UDP) data to transmit over a packet network likethe Internet. The connection unit 110 converts the upper data loaded ona TCP data or a UDP data into a data appropriate to the Internet.

FIG. 2 is a diagram illustrating the constitution of a T.38 packet. Asshown in FIG. 2, a T.38 packet is formed of a sequence number 200, aprimary message 210, an error control method option field 220, asecondary message sequence length 230, and secondary message sequences240, 250, 260, and 270. Since the elements of the T.38 packet are wellknown to those skilled in the art, descriptions about the elements ofthe T.38 packet will be omitted.

Error control methods include a redundancy method and a forward errorcorrection (FEC) method. Here, the error control method is determined bythe value of the error control method option field 220 of the T.38packet of FIG. 2. Therefore, the secondary message sequences are filledwith redundancy messages 240 and 250 or FEC messages 260 and 270.

The secondary message sequence length 230, establishing the length ofthe secondary message sequences, denotes the length of the redundancymessages 240 and 250 or the FEC messages 260 and 270. When the secondarymessage sequence length 230 increases, an error control performanceimproves. In particular, in the case where the FEC error control methodis used, a burst error can be corrected by increasing the secondarymessage sequence length 230.

However, in a conventional error control method, an error control methodoption field 220 and a secondary message sequence length 230 aredetermined by a manager in an early stage and not changed regardless ofchanges in the status of a network through which a T.38 fax data istransmitted, thereby causing inefficiency. In other words, when thestatus of the network is good, a secondary message sequence lengthbecomes so excessively large that a transmission speed is deteriorated.When the status of the network is bad, the secondary message sequencelength becomes so relatively small that errors are likely to occur.

An improved method for correcting errors in a communication betweengateways 100 of FIG. 1 will be described as follows. FIG. 3 illustratesan RR message type of an RTCP in transmitting and receiving an Internetfax data between gateways and FIG. 4 illustrates a method forcontrolling errors of an Internet fax data according to the presentinvention.

With reference to FIG. 3, a transmission gateway 300 transmits a T.38fax data to a reception gateway 310 and the reception gateway 310transfers status information on the T.38 fax data as an RR message of anRTCP. Here, since the contents of the RR message 320 is well known tothose skilled in the art, detailed description about the RR message 320will be omitted.

The fields of ordinary messages of an RTCP, for example, a sender report(SR), an RR, an SDES, and a BYE, are related to a real-time transportprotocol (RTP) packet. However, in the case where an Internet fax datais transmitted and received, a fax packet is loaded on an UDP and not onan RTP so that an RTP packet is not generated. Consequently, in a methodfor controlling errors according to the present invention, the secondprotocol process unit 150 relates the internal field of an RTCP messageto a T.38 packet so as to operate the RTCP message with the thirdprotocol process unit 160, in transmitting an Internet fax data.

A procedure of a method for controlling errors will now be described indetail. A transmission gateway 300 having initially established methodfor controlling errors and secondary message sequence length transmits aT.38 fax data in step 410. A reception gateway 310 receives the T.38 faxdata while a third protocol process unit 170 monitors the QoS of theT.38 fax data in step 420. The third protocol process unit 170 loads apacket loss number of the received T.38 fax data on a fraction lostfield of an RR message 320 and transmits the packet loss number to thetransmission gateway 300 in step 430.

When the transmission gateway 300 receives the RR message 320 whiletransmitting the T.38 fax data by using the initially established methodfor controlling errors and secondary message sequence length, thetransmission gateway 300 reads out and analyzes the value the fractionlost field in step 440. According to the analysis results, it isdetermined whether the T.38 fax data packet transmitted from thetransmission gateway 300 has been lost in step 450. If the T.38 fax datapacket has been lost, the secondary message sequence length 230 isincreased by one in step 470. If the T.38 fax data packet has not beenlost, the secondary message sequence length 230 is decreased by one instep 460. Then, the T.38 fax data is transmitted in step 480.

A method for controlling errors of an Internet fax data according to thepresent invention can be realized as a code on a recording medium whichcan be read out by a computer. Here, the recording medium includes anykind of recording devices in which data are recorded, such as ROM, RAM,CD-ROM, a magnetic tape, a floppy disk, and an optical data recordingdevice, while further including a carrier wave, i.e., transmission overthe Internet. In addition, the recording media read out by a computerare distributed to computer systems, connected by a network, to recordand execute codes, which can be read out by a computer, in adistribution manner.

It is noted that the present invention is not limited to the preferredembodiment described above, and it is apparent that variations andmodifications by those skilled in the art can be effected within thespirit and scope of the present invention defined in the appendedclaims.

As described above, a method for controlling errors of an Internet faxdata according to the present invention can control errors of a T.38packet in real time, according to the status of a network, intransmitting a T.38 fax data over the Internet. Therefore, theperformance of an error control improves, thereby securing a stablecommunication and improving a transmission speed. As a result, acommunication speed increases so that transmission efficiency improves.

1. A gateway for a fax on Internet protocol (FoIP), the gatewaycomprising: a first protocol process unit transmitting and receiving anH.323 call setup data; a second protocol process unit generating statusinformation on a fax data based on the fax data transmitted and receivedbetween gateways by using a real-time transport protocol; a thirdprotocol process unit receiving the status information for analyzing thestatus of a network and selecting a method for controlling errors; and aconnection unit converting a predetermined protocol data for the FoIPincluding the H.323 call setup data into a data architecture appropriateto a packet switching network for transmitting and receiving theconverted data to and from the packet switching network.
 2. The gatewayfor an FoIP of claim 1, wherein the third protocol process unit furtherincludes a fourth protocol process unit performing conversion between aT.30 data processed by a T.30 protocol and a T.38 data processed by aT.38 protocol.
 3. The gateway for an FoIP of claim 1, wherein theconnection unit converts a predetermined protocol data for the FoIP intoa data architecture formed by at least one protocol of a transmissioncontrol protocol (TCP) or a user datagram protocol (UDP).
 4. The gatewayfor an FoIP of claim 3, wherein the connection unit converts the dataarchitecture into a data architecture appropriate to the Internet.